Supported osmates, process for preparation thereof, and a process for the preparation of chiral vicinal diols using supported osmate catalyst

ABSTRACT

The present invention provides a supported osmate useful as a reusable catalyst in the preparation of vicinal diols. The present invention also relates to a process for the preparation of supported osmates of the formula (S—NR 3 ) 2 OsO 4 .nH 2 O wherein S is a support, R is an alkyl group, n is the number of water molecules and use thereof in the preparation of vicinal diols by asymmetric dihydroxylation (AD) of olefins in presence of cinchona alkaloid compounds.

FIELD OF THE INVENTION

[0001] The present invention relates to a supported osmate useful as areusable catalyst in the preparation of vicinal diols. The presentinvention also relates to a process for the preparation of supportedosmates of the formula (S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is analkyl group, n is the number of water molecules and use thereof in thepreparation of vicinal diols by asymmetric dihydroxylation (AD) ofolefins in presence of cinchona alkaloid compounds.

BACKGROUND OF THE INVENTION

[0002] Asymmetric dihydroxylation of olefins in the presence of cinchonaalkaloid results in products that are important intermediates in thepreparation of various drugs and chemicals. For example, the products ofcinnamic acid esters are intermediates for taxol side chain, ananticancer drug, diltiazem, calcium antagonist and chloramphenicol, anantibiotic. Proranolol, a β blocker can also be derived from diolsobtained through this method.

[0003] There are serious disadvantages in performing the catalytic ADreaction with homogeneous system in the manufacture of vicinal diols dueto presence of toxic remnants of osmium in products and high cost ofosmium tetraoxide or potassium osmate dihydrate. By employing theheterogeneous catalytic system, the cost naturally comes down due toeasy recovery of the catalyst and very insignificant loss of osmiumtetraoxide, when compared with homogeneous system. The products thusobtained using heterogeneous catalyst system are benign in the sensethat the presence of osmium in minor impurities in the dihydroxylatedproducts is also precluded.

[0004] U.S. Pat. Nos. 4,871,855 and 5,260,421 disclose processes forasymmetric dihydroxylation of olefins using osmium tetraoxide andcinchona alkaloids using homogenous catalyst systems. These processesinvolve cumbersome recovery of the osmium catalyst from the reactionmixture, generation of toxic waste and the potential presence of toxicosmium in the product.

[0005] U.S. Pat. Nos. 5,516,929 and 5,260,461 disclose asymmetricdihydroxylation of olefins using osmium tetraoxide and polymer boundcinchona alkaloids in a heterogeneous system. The quantitative recoveryof the toxic osmium catalyst, lower enantioselectivity and reduction inactivity and enantioselectivity in each recycle experiments are some ofthe disadvantages associated with this process.

[0006] U.S. Pat. No. 5,968,867 discloses asymmetric dihydroxylation ofolefins using osmium tetraoxide and silica gel supported bis-cinchonaalkaloid derivatives in a heterogeneous system. Quantitative recovery oftoxic osmium catalyst is difficult and a reduction in activity andenantioselectivity of the catalyst is observed in each and every recycleexperiment.

[0007] European Patent 940,170 A2 describes the catalytic asymmetricdihydroxylation of alkenes using a polymer supported osmium catalyst.The drawbacks of this process are that higher amounts of catalyst arerequired (5 mol %), the reaction time is very long and expensivepolymers are used as supports.

OBJECTS OF THE INVENTION

[0008] The main object of the invention is to provide a heterogeneousrecyclable supported osmate of the general formula (S—NR₃)₂OsO₄.nH₂Owherein S is a support, R is an alkyl group, n is the number of watermolecules and use thereof in the preparation of vicinal diols byasymmetric dihydroxylation (AD) of olefins in presence of cinchonaalkaloid compounds.

[0009] It is another object of the invention to provide a process forthe preparation of a novel heterogeneous recyclable supported osmate ofthe general formula (S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is analkyl group, n is the number of water molecules and use thereof in thepreparation of vicinal diols.

[0010] It is another object of the invention to provide aenvironmentally friendly process for the asymmetric dihydroxylation ofolefins to obtain vicinal diols using a novel heterogeneous supportedosmate of the invention.

[0011] It is a further object of the invention to provide a process forthe preparation of vicinal diols with good enantioselectivity, activityand yield by the asymmetric dihydroxylation of olefins using a novelosmate catalyst of the invention.

[0012] It is yet another object of the invention to provide a processfor the preparation of vicinal diols by the asymmetric dihydroxylationof olefins in the presence of cinchona alkaloids and derivativesthereof, which process is simple, economical and results in a productwith no traces of toxic osmium therein.

[0013] It is a further object of the invention to provide a process forthe preparation of vicinal diols by the asymmetric dihydroxylation ofolefins in the presence of cinchona alkaloids and derivatives thereofwherein the catalyst is capable of recycle several times withoutsubstantial loss of activity or in yield of product.

SUMMARY OF THE INVENTION

[0014] These and other objects of the invention are achieved by usingthe novel supported heterogeneous osmate catalyst of the general formulaS—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules for the asymmetric dihydroxylation of olefinsin the presence of cinchona alkaloids to obtain vicinal diols with goodyield and selectivity.

[0015] The novelty of the invention lies in the supported osmatecatalyst and in preparation of vicinal diols in presence of cinchonaalkaloids or derivatives employing oxidants.

[0016] Accordingly, the present invention provides a supported osmate ofthe general formula S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is analkyl group, n is the number of water molecules.

[0017] In one embodiment of the invention, the support is selected fromresin and silica.

[0018] In another embodiment of the invention, R is selected frommethyl, ethyl, propyl, butyl and like alkyl groups.

[0019] In a further embodiment of the invention, the osmium content inthe catalyst is in the range of 1 to 30%.

[0020] In a further embodiment of the invention, the support S assynthesized has charge balancing anions selected from chloride, bromide,iodide, fluoride, hydroxide and acetate.

[0021] The invention also relates to a process for the preparation of anovel heterogeneous supported osmate catalyst of the formulaS—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules, said process comprising reacting potassiumosmate with a quaternary ammonium species in water.

[0022] In one embodiment of the invention, the potassium osmate is ofthe formula K₂OsO₄2H₂O.

[0023] In another embodiment of the invention, the quaternary ammoniumspecies is of the formula S—NR₃X wherein S is a support, R is alkyl andX is selected from Cl, Br, I, F, —OH and OAc.

[0024] In a further embodiment of the invention, the reaction is carriedout at a temperature in the range of 25 to 100° C. for a period in therange of 5-24 hours.

[0025] In one embodiment of the invention, the osmium content in thecatalyst is in the range of 1 to 30%.

[0026] In another embodiment of the invention, the support S is selectedfrom resin and silica.

[0027] In a further embodiment of the invention, the support S assynthesized has charge balancing anions selected from chloride, bromide,iodide, fluoride, hydroxide and acetate.

[0028] In another embodiment of the invention, R is selected frommethyl, ethyl, propyl, butyl and like alkyl groups.

[0029] The present invention also provides a process for the preparationof vicinal diols comprising asymmetrically dihydroxylating thecorresponding olefin in the presence of a cinchona alkaloid using anoxidant in a solvent selected from the group consisting of water,acetone, acetonitrile, t-butanol and any mixture thereof, at atemperature in the range of −70 to 100° C. for a period in the range of0.5 to 24 hours, and in the presence of a catalytic amount of aheterogeneous supported osmate catalyst of the general formulaS—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules, and recovering the pure vicinal diol.

[0030] In one embodiment of the invention, the osmium content in thecatalyst is in the range of 1 to 30%.

[0031] In another embodiment of the invention, the support S is selectedfrom resin and silica.

[0032] In a further embodiment of the invention, the support S used hascharge balancing anions selected from chloride, bromide, iodide,fluoride, hydroxide and acetate.

[0033] In another embodiment of the invention, R is selected frommethyl, ethyl, propyl, butyl and like alkyl groups.

[0034] In yet another embodiment of the invention, the amount ofsupported osmate used in the reaction is 0.01 to 10 mol % of osmiumcontent with respect to the substrate.

[0035] In yet another embodiment of the invention the solvent usedcomprises a solvent system selected from the group consisting ofwater:acetone, water:acetonitrile and water:t-butanol, the ratio ofwater to acetone, acetonitrile and t-butanol being in the range of 1:1to 1:3, and water:acetone:acetonitrile in a ratio of 1:1:1.

[0036] In another embodiment of the invention, the catalyst is recoveredfrom the reaction system and recycled to the reaction system as manytimes as desired.

[0037] In a further embodiment of the invention, the oxidant used isselected from the group consisting of N-methylmorpholine N-oxide (NMO),trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide,potassium ferricyanide, sodium periodate and molecular oxygen.

[0038] In yet another embodiment of the invention, the cinchona alkaloidand derivatives thereof comprise a monomeric and polymeric chiralligand.

[0039] In a further embodiment of the invention, the chiral ligand isselected from the group consisting of (DHQD)₂PHAL, (DHQD)₂PYR,(DHQD)₂AQN, DHQD-OAc, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND andpseudoenantiomeric forms thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0040] The novelty of the invention lies in the supported osmatecatalyst and in preparation of vicinal diols in the presence of cinchonaalkaloids or derivatives employing oxidants.

[0041] The novel supported osmate is of the general formula(S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules. The support is preferably selected from resinor silica R is preferably selected from methyl, ethyl, propyl, butyl andlike alkyl groups. The osmium content in the catalyst is generally inthe range of 1 to 30%. The support S as synthesized may contain chargebalancing anions selected from chloride, bromide, iodide, fluoride,hydroxide and acetate.

[0042] The heterogeneous osmate catalyst of the general formula(S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, n is thenumber of water molecules is prepared by reacting potassium osmate withsupported quaternary ammonium species in water as a solvent at atemperature in the range of 25 to 100° C. for a period in the range of5-24 hours to obtain the desired catalyst.

[0043] The process for preparation of vicinal diols comprisesasymmetrically dihydroxylating the corresponding olefin in the presenceof a cinchona alkaloid compound using an oxidant in a solvent selectedfrom the group consisting of water, acetone, acetonitrile, t-butanol andany mixture thereof at a temperature in the range of −70 to 100° C. fora period in the range of 0.5 to 24 hours, and in the presence of acatalytic amount of a heterogeneous supported osmate catalyst of thegeneral formula (S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkylgroup, n is the number of water molecules, and recovering the purevicinal diol by any conventional method. The amount of supported osmateused in the reaction is 0.01 to 10 mol % of osmium content with respectto the substrate.

[0044] The catalyst can be recovered from the reaction system by anyconventional process and recycled to the reaction system several timeswithout any substantial loss of activity or of yield of the product. Theoxidant used is selected from N-methylmorpholine N-oxide (NMO),trimethylamine N-oxide, hydrogen peroxide, t-butyl hydrogen peroxide,potassium ferricyanide, sodium periodate and molecular oxygen. Thecinchona alkaloid and derivatives thereof comprise a monomeric andpolymeric chiral ligand such as for example (DHQD)₂PHAL, (DHQD)₂PYR,(DHQD)₂AQN, DHQD-OAc, DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND andpseudoenantiomeric forms thereof.

[0045] Scientific Explanation

[0046] In the present invention, novel supported osmates were preparedfor the first time using the anion exchange method from the supportedquaternary ammonium species. The osmate anions present on the supportare responsible for the dihydroxylation activity of the reaction. Theactivity of the supported osmate is similar or higher than thehomogeneous counterparts. Without wishing to be bound by any theory, itis believed that the higher activity is ascribed to the support effect.The large positive potential of OsO₄ ²⁻ support surface inducespolarisation of N→O bond and facilitates oxygen transfer.

[0047] Higher yields and enantioselectivities are obtained withsupported osmate catalysts used in the asymmetric dihydroxylation ofolefins in aqueous organic solvents. Since the dihydroxylated productsare important intermediates for the preparation of drugs andpharmaceuticals, this invention is timely and appropriate. Therefore,supported osmate is a better option for the synthesis of vicinol diols.The supported osmate catalysts prepared from various supports offeredgood yields and enantioselectivies in presence of cinchona alkaloids.Thus this invention offers the best techno-economic route for thesynthesis of vicinol diols, intermediates for the preparation of drugsand pharmaceuticals.

[0048] Supported osmates are prepared as exemplified and used incatalytic amounts for preparing vicinol diols by asymmetricdihydroxylation of olefins employing oxidants in presence of cinchonaalkaloid compounds in a heterogeneous manner as described.

[0049] The following examples are given by way of illustration of thepresent invention and therefore should not be construed to limit thescope of the invention.

[0050] Preparation of Catalysts

EXAMPLE 1

[0051] Resin-OsO₄: Resin was obtained by quaternization of triethylamine(2.1 mL, 21 mmol) with 1 g of chloromethylated styrene-divinylbenzenecopolymer (Merrifield resin, capacity-2.1 mequiv/g) in chloroform (20mL) under reflux for 24 h. 1 g of quaternary ammonium resin wassuspended in 100 mL of 0.8 mmol aqueous potassium osmate solution andstirred at 25° C. for 12 h under nitrogen atmosphere. The solid catalystwas filtered, washed thoroughly with 300 mL of water and vacuum dried toobtain Resin-OsO₄ (0.641 mmol of Os per g).

EXAMPLE 2

[0052] SiO₂—OsO₄: Modified silica was obtained by quaternisation oftriethylamine (0.7 mL, 7 mmol) with bromopropylsilica (capacity 0.7mequiv/g) in chloroform (20 mL) under reflux for 24 h. 1 g of quaternaryammonium silica was suspended in 100 mL of 0.33 mmol aqueous potassiumosmate solution and stirred at 25° C. for 12 h under nitrogenatmosphere. The solid catalyst was filtered, washed thoroughly with 300mL of water and vacuum dried to obtain SiO₂—OsO₄ (0.317 mmol of Os perg).

[0053] Asymmetric Dihydroxylation of Olefins

[0054] The asymmetric dihydroxylation reaction of olefins was performedusing the following method in order to evaluate supported osmates of thepresent invention.

[0055] Supported osmate (0.01 eq. wt. of osmium content), bis-cinchonaalkaloid (DHQD)₂PHAL (0.01 Eq. Wt.) and N-methylmorpholine-N-oxide (1.5Eq. Wt.) were stirred in the mixed solvent of water/acetone/acetonitrile(in the volume ratio of 1:1:1). To this mixture was added an olefin (1.0Eq. Wt) slowly for a period of 12 h. After the reaction, the supportedosmate catalyst was filtered off and washed with ethyl acetate. Thecombined filtrates were concentrated under reduced pressure. The chiralligand was recovered from the aqueous layer after acidification (1NHCl). The concentrated organic layer was purified to afford thecorresponding cis-diol by using conventional processes. The yield andthe optical purity of the product were determined.

[0056] Catalytic Asymmetric Dihydroxylation of Olefins UsingN-Methylmorpholine-N-Oxide as a Co-Oxidant

EXAMPLE 3

[0057] Catalytic Asymmetric Dihydroxylation Reaction of Trans-Stilbeneby Using Resin-OsO₄:

[0058] Resin-OsO₄(0.01 eq wt), Hydroquinidine 1,4-phthalazinediyldiether (DHQD)₂PHAL (0.01 eq. wt.) and N-methylmorpholine-N-oxide (1.5eq. wt.) were stirred in mixed solvent of water/acetone/acetonitrile(volume ratio of 1:1:1). To this mixture trans-stilbene (1.0 eq. wt) wasadded and stirred at room temperature for 6 hours. After the reaction,supported osmate catalyst was filtered off and washed with methanol.Combined filtrates were concentrated under reduced pressure. Chiralligand was recovered from aqueous layer after acidification (1N HCl).Pure product was obtained by removing solvent at reduced pressurefollowed by column chromatography.

[0059] (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 96%)

[0060] [∝]_(D)+92.44 (c 1.0, EtOH): e.e.=99.4%

[0061] Catalyst Reusability Experiments

EXAMPLE 4

[0062] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby using Resin-OsO₄ which had been used in Example 3 without furtheraddition of osmate catalyst.

[0063] The reaction was performed using identical process as in Example3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 95%) [∝]_(D)+92.90 (c 1.0,EtOH): e.e.=99.9%

EXAMPLE 5

[0064] Catalytic asymmetric dihydroxylation reaction of trans stilbeneby using Resin-OsO₄ which had been used in Example 4 without furtheraddition of supported osmate catalyst.

[0065] The reaction was performed by using an identical process as inExample 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 97%)

[0066] [∝]_(D)+92.16 (c 1.0, EtOH): e.e.=99.1%

EXAMPLE 6

[0067] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby using Resin-OsO₄ which had been used in Example 5 without furtheraddition of supported osmate catalyst.

[0068] The reaction was performed by using identical process as inExample 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 94%)

[0069] [∝]_(D)+92.25 (c 1.0, EtOH): e.e.=99.2%

EXAMPLE 7

[0070] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby using Resin-OsO₄ which had been used in Example 6 without furtheraddition of Supported osmate catalyst.

[0071] The reaction was performed by using an identical process as inExample 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 96%)

[0072] [∝]_(D)+92.81 (c 1.0, EtOH): e.e.=99.8%

EXAMPLE 8

[0073] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby using Resin-OsO₄ which had been used in Example 7 without furtheraddition of supported osmate catalyst.

[0074] The reaction was performed by using an identical process as inExample 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 98%)

[0075] [∝]_(D)+92.25 (c 1.0, EtOH): e.e.=99.2%

EXAMPLE 9

[0076] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby SiO₂-OsO₄

[0077] The reaction was performed by using an identical process as inExample 3. (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% ofenantiomeric excess was obtained (yield 97%)

[0078] [∝]_(D)+92.34 (c 1.0, EtOH): e.e.=99.3%

EXAMPLE 10

[0079] Catalytic asymmetric dihydroxylation reaction of styrene by usingResin-OsO₄

[0080] The reaction was performed by using an identical process as inExample 3 except slow addition of olefin with a reaction time of 12hours. (R)-phenyl-1,2-ethanediol of more than 95.0% of enantiomericexcess was obtained (yield 94%) [α]_(D) −34.29 (c 1.32, EtOH):e.e.=95.7%

EXAMPLE 11

[0081] Catalytic asymmetric dihydroxylation reaction oftrans-beta-methyl styrene by using Resin-OsO₄

[0082] The reaction was performed by using an identical process as inExample 3 except slow addition of olefin with a reaction time of 12hours. (R,R)-1-phenyl-1,2-propanediol of more than 98.0% of enantiomericexcess was obtained (yield 97%)

[0083] [∝]_(D) −30.50 (c 1.32, EtOH): e.e.=98.1%

EXAMPLE 12

[0084] Catalytic asymmetric dihydroxylation reaction of methyltrans-cinnamate by using Resin-OsO₄.

[0085] The reaction was performed by using an identical process as inExample 3 except slow addition of olefin with a reaction time of 12hours. (2S,3R)-2,3-dihydroxy-3-phenylpropionate of more than 99% ofenantiomeric excess was obtained (yield 96%)

[0086] [≢]_(D) −10.6 (c 1.0, CHCl₃): e.e.=99%

EXAMPLE 13

[0087] Catalytic asymmetric dihydroxylation reaction of allyl 1-naphthylether by using Resin-OsO₄

[0088] The reaction was performed by using an identical process as inExample 3 except slow addition of olefin with a reaction time of 12hours. 2,3-dihydroxypropyl-1-naphthyl ether of more than 77.0% ofenantiomeric excess was obtained (yield 94%)

[0089] [∝]_(D) +5.18 (c 1.0, CH₃OH): e.e.=77.4%

EXAMPLE 14

[0090] Catalytic dihydroxylation reaction of trans-stilbene by usingResin-OsO₄:

[0091] Resin-OsO₄ (0.01 Eq. Wt.), N-methylmorpholine-N-oxide (1.5 Eq.Wt.) and trans-stilbene (1.0 Eq. Wt) in the mixed solvent ofwater/acetone/acetonitrile (in the volume ratio of 1:1:1) were stirredat room temperature for 6 hours. After completion of the reaction, thecatalyst was filtered off and washed with ethyl acetate. Combinedfiltrates were concentrated under reduced pressure. The pure product,1,2-diphenyl-1,2-ethandiol was obtained by removing the solvent reducedpressure followed by column chromatography. (yield 93%).

[0092] The experimental results in the Examples 3 to 14 are tabulated inTables 1 and 2. TABLE 1 Reuse of Resin-OsO₄ for asymmetricdihydroxylation reaction of trans-stilbene Ex.No run Yield ee 3 1 9699.4 4 2 95 99.9 5 3 97 99.1 6 4 94 99.2 7 5 96 99.8 8 6 98 99.2

[0093] TABLE 2 Catalytic asymmetric dihydroxylation reaction of olefinsby using Resin-OsO₄ Ex.No Catalyst^(a) Ligand Olefin Time Yield^(b)ee^(c) Config.^(d)  9 SiO₂—OsO₄ (DHQD)₂PHAL Trans-stilbene 6 97 99.3 RR10 Resin-OsO₄ (DHQD)₂PHAL Styrene 12 94 95.7 R 11 Resin-OsO₄ (DHQD)₂PHALE-Methylstyrene 12 97 98.1 RR 12 Resin-OsO₄ (DHQD)₂PHAL E- 12 96 99.02S, 3R Methylcinnamate 13 Resin-OsO₄ (DHQD)₂PHAL Allyl 1-naphrhyl 12 9477.4 S ether 14 Resin-OsO₄ — Trans-stilbene 6 93 — —

EXAMPLE 15

[0094] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby Resin-OsO₄:

[0095] The reaction was performed by an identical process as in Example3 except the solvent is water/acetone (in the volume ratio of 1:3).(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 95%)

[0096] [∝]_(D) +91.90 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 16

[0097] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby Resin-OsO₄:

[0098] The reaction was performed by an identical process as in Example3 except the solvent is water/acetonitrile (in the volume ratio of 1:3).(R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than 99.0% of enantiomericexcess was obtained (yield 93%)

[0099] [α]_(D) +91.1 (C 1.0, EtOH): e.e.=99.0%

EXAMPLE 17

[0100] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby Resin-OsO₄:

[0101] The reaction was performed by an identical process as in Example3 except the solvent is water/t-butanol (volume ratio of 1:3) and thereaction time is 24 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 91%)

[0102] [∝]_(D) +91.6 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 18

[0103] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby Resin-OsO₄:

[0104] The reaction was performed by an identical process as in Example3 except the solvent is water/t-butanol (volume ratio of 1:2) and thereaction time is 24 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 90%)

[0105] [∝]_(D) +92.1 (c 1.0, EtOH): e.e.=99.0%

EXAMPLE 19

[0106] Catalytic asymmetric dihydroxylation reaction of trans-stilbeneby Resin-OsO₄:

[0107] The reaction was performed by an identical process as in Example3 except the solvent is water/t-butanol (volume ratio of 1:1) and thereaction time is 36 h (R,R)-(+)-1,2-diphenyl-1,2-ethandiol of more than99.0% of enantiomeric excess was obtained (yield 92%)

[0108] [∝]_(D) +92.3 (c 1.0, EtOH): e.e.=99.0% TABLE 3 Solvent effectsin catalytic asymmetric dihydroxylation reaction of trans-stilbene byResin-OsO₄ Ex. No Catalyst^(a) Ligand Olefin Time Yield^(b) ee^(c)Config.^(d) 15 Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 6 95 99 RR 16Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 6 93 99 RR 17 Resin-OsO₄(DHQD)₂PHAL Trans-stilbene 24 91 99 RR 18 Resin-OsO₄ (DHQD)₂PHALTrans-stilbene 24 90 99 RR 19 Resin-OsO₄ (DHQD)₂PHAL Trans-stilbene 3692 99 RR

[0109] The main advantages of the present invention are:

[0110] 1. A novel and ecofriendly process for asymmetric dihydroxylationof olefins is presented.

[0111] 2. The present process dispenses the use of soluble, toxic osmiumtetraoxide or potassium osmate dihydrate instead heterogeneous reusablesupported osmates are used.

[0112] 3. Supported osmates are prepared and used for asymmetricdihydroxylation of olefins as heterogeneous catalysts. The use ofheterogeneous supported osmates precludes the presence of osmium intraces with product.

[0113] 4. The enantioselectivity and the yields are good.

[0114] 5. The work-up procedure is simple.

[0115] 6. The catalyst is subjected to many recycles, which displayedconsistent activity.

[0116] 7. The present process is environmentally safe since there is nodisposal problem.

[0117] 8. The process is economical

We claim:
 1. A supported osmate of the general formula S—NR₃)₂OsO₄.nH₂Owherein S is a support, R is an alkyl group, n is the number of watermolecules.
 2. A supported osmate as claimed in claim 1 wherein thesupport S is selected from resin and silica.
 3. A supported osmate asclaimed in claim 1 wherein R is selected from methyl, ethyl, propyl,butyl and like alkyl groups.
 4. A supported osmate as claimed in claim 1wherein the osmium content in the catalyst is in the range of 1 to 30%.5. A supported osmate as claimed in claim 1 wherein the support S assynthesized has charge balancing anions selected from chloride, bromide,iodide, fluoride, hydroxide and acetate.
 6. A process for thepreparation of a novel heterogeneous supported osmate catalyst of theformula S—NR₃)₂OsO₄.nH₂O wherein S is a support, R is an alkyl group, nis the number of water molecules, said process comprising reactingpotassium osmate with a quaternary ammonium species in water.
 7. Aprocess as claimed in claim 6 wherein the potassium osmate is of theformula K₂OsO₄2H₂O.
 8. A process as claimed in claim 6 wherein thequaternary ammonium species is of the formula S—NR₃X wherein S is asupport, R is alkyl, and X is selected from Cl, Br, I, F, —OH and OAc.9. A process as claimed in claim 6 wherein the reaction is carried outat a temperature in the range of 25 to 100° C. for a period in the rangeof 5-24 hours.
 10. A process as claimed in claim 6 wherein the osmiumcontent in the catalyst is in the range of 1 to 30%.
 11. A process asclaimed in claim 6 wherein the support S is selected from resin andsilica.
 12. A process as claimed in claim 6 wherein the support S assynthesized has charge balancing anions selected from chloride, bromide,iodide, fluoride, hydroxide and acetate.
 13. A process as claimed inclaim 6 wherein R is selected from methyl, ethyl, propyl, butyl and likealkyl groups.
 14. A process for the preparation of vicinal diolscomprising asymmetrically dihydroxylating the corresponding olefin inthe presence of a cinchona alkaloid using an oxidant in a solventselected from the group consisting of water, acetone, acetonitrile,t-butanol and any mixture thereof at a temperature in the range of −70to 100° C. for a period in the range of 0.5 to 24 hours, and in thepresence of a catalytic amount of a heterogeneous supported osmatecatalyst of the general formula S—NR₃)₂OsO₄.nH₂O wherein S is a support,R is an alkyl group, n is the number of water molecules, and recoveringthe pure vicinal diol.
 15. A process as claimed in claim 14 wherein theosmium content in the catalyst is in the range of 1 to 30%.
 16. Aprocess as claimed in claim 14 wherein the support S is selected fromresin and silica.
 17. A process as claimed in claim 14 wherein thesupport S used has charge balancing anions selected from chloride,bromide, iodide, fluoride, hydroxide and acetate.
 18. A process asclaimed in claim 14 wherein R is selected from methyl, ethyl, propyl,butyl and like alkyl groups.
 19. A process as claimed in claim 14wherein the amount of supported osmate used in the reaction is 0.01 to10 mol % of osmium content with respect to the substrate.
 20. A processas claimed in claim 14 wherein the solvent used comprises a solventsystem selected from the group consisting of water:acetone,water:acetonitrile and water:t-butanol, the ratio of water to acetone,acetonitrile and t-butanol being in the range of 1:1 to 1:3, andwater:acetone:acetonitrile in a ratio of 1:1:1.
 21. A process as claimedin claim 14 wherein the catalyst is recovered from the reaction systemand recycled to the reaction system as many times as desired.
 22. Aprocess as claimed in claim 14 wherein the oxidant used is selected fromthe group consisting of N-methylmorpholine N-oxide (NMO), trimethylamineN-oxide, hydrogen peroxide, t-butyl hydrogen peroxide, potassiumferricyanide, sodium periodate and molecular oxygen.
 23. A process asclaimed in claim 14 wherein the cinchona alkaloid and derivativesthereof comprise a monomeric and polymeric chiral ligand.
 24. A processas claimed in claim 23 wherein the chiral ligand is selected from thegroup consisting of (DHQD)₂PHAL, (DHQD)₂PYR, (DHQD)₂AQN, DHQD-OAC,DHQD-CLB, DHQD-PHN, DHQD-MEQ, DHQD-IND and pseudoenantiomeric formsthereof.